/* Licensed under BSD-MIT - see LICENSE file for details */
#include <stdio.h>
#include <stdlib.h>
#include "list.h"

static void *corrupt(const char *abortstr,
             const struct list_node *head,
             const struct list_node *node,
             unsigned int count)
{
    if (abortstr) {
        fprintf(stderr,
            "%s: prev corrupt in node %p (%u) of %p\n",
            abortstr, node, count, head);
        abort();
    }
    return NULL;
}

struct list_node *list_check_node(const struct list_node *node,
                  const char *abortstr)
{
    const struct list_node *p, *n;
    int count = 0;

    for (p = node, n = node->next; n != node; p = n, n = n->next) {
        count++;
        if (n->prev != p)
            return corrupt(abortstr, node, n, count);
    }
    /* Check prev on head node. */
    if (node->prev != p)
        return corrupt(abortstr, node, node, 0);

    return (struct list_node *)node;
}

struct list_head *list_check(const struct list_head *h, const char *abortstr)
{
    if (!list_check_node(&h->n, abortstr))
        return NULL;
    return (struct list_head *)h;
}
